The corner stone of Darwin's theory is :

Options

A. Inheritance of acquired character
B. Higher productivity
C. Natural selection
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the cornerstone of Darwin's theory. This means we need to identify the central concept that underpins his ideas about evolution.

2. **Identifying Options**: The options provided include:
- Inheritance of Equal Characters (Lamarck's theory)
- Higher Productivity (an ecological concept)
- Natural Selection (Darwin's theory)

3. **Evaluating the First Option**: The Inheritance of Equal Characters is associated with Lamarck, who proposed that traits acquired during an organism's lifetime can be passed on to offspring. This is not a cornerstone of Darwin's theory.

4. **Evaluating the Second Option**: Higher Productivity refers to the productivity of autotrophs in an ecosystem and does not pertain directly to Darwin's theory of evolution. Thus, it is not the cornerstone of his work.

5. **Evaluating the Third Option**: Natural Selection is the principle that Darwin proposed, stating that organisms that are better adapted to their environment are more likely to survive and reproduce. This concept is often summarized by the phrase "survival of the fittest."

6. **Conclusion**: Based on the evaluation, the cornerstone of Darwin's theory is Natural Selection. This principle explains how species evolve over time through the process of adaptation to their environments.

**Final Answer**: The cornerstone of Darwin's theory is Natural Selection.

---